1. Field of the Invention
The present invention relates to a flow control valve employed in a refrigerating cycle, and more particularly, to a flow control valve using a direct current(DC) motor for improving the control of flow, and its durability.
2. Description of the Related Arts
Generally, a refrigerating cycle comprises an evaporator, a compressor, a condenser, an expansion valve, etc., and decreases the temperature of its surrounding environment by the mechanism of evaporation, compression, condensation, and expansion of coolant.
Describing the mechanism in more detail, the liquefied coolant inside the evaporator of the refrigerating cycle is evaporated by taking latent heat needed for its evaporation from the air around a cooling line. Then, the air is cooled down, its temperature decreased after its latent heat being taken, thereby maintaining the interior of, for example, a refrigerator operated by the refrigerating cycle at low temperature by its natural circulation or by the operation of a certain fan. The coolant supplied from an expansion valve and the evaporated coolant vapor exist together inside the evaporator, and during the phase transition from the liquid state to the vapor state, there is a certain relation between the pressure and the temperature of the evaporation.
The coolant vapor evaporated from the evaporator is supplied to the compressor to facilitate continuous evaporation of the liquefied coolant even under a low temperature by maintaining a low pressure inside the evaporator. Then, the coolant vapor supplied to the compressor is compressed by a piston of a cylinder so that it becomes easily liquefied because of its increased pressure even by cooling it by a cooling water or a cooling air at room temperature.
Then, the compressed coolant from the compressor is cooled, condensed, and liquefied at the condenser. The condensation at the condenser also occurs in the state that the liquefied coolant and the evaporated coolant exist together like in the above evaporation. During the phase transition from vapor to liquid, there is a certain relation between the pressure and the temperature of the condensation.
Expansion is performed to reduce the pressure of the liquefied coolant by the condenser enough to be easily evaporated in advance before supplying the liquefied coolant to the evaporator. An expansion valve functions to reduce the pressure, which is the expansion, and also to control the flow of the liquefied coolant. That is, the amount of the liquefied coolant to be evaporated inside the evaporator is determined according to the heat amount to be taken away from the interior of a refrigerator, the evaporation temperature and the evaporation pressure. It is very important to supply the proper amount of the liquefied coolant to the evaporator, exactly controlling it so as not to be over/short-supplied.
That is, the expansion valve adiabatically expands the liquefied coolant at a high temperature and a high pressure to the state of a low temperature and a low pressure by the throttling operation and functions as a flow control valve to maintain a supply amount of the liquefied coolant at a certain level according to the load of the evaporator.
Many types of the expansion valves that are commercially known vary the controlling method and structure. Recently, throttling of the flow control valve is widely known because of its high operation capability, fine control, and reduced manufacturing expenses, etc.
One typical embodiment thereof is described herein after with reference of the drawings.
As shown in FIG. 1, the flow control valve comprises a cap 1 having a certain shape, a heating bottom plate 3, which is made of ceramic material, and has an expansion agent opening 2 on both sides, an Al-electrode 5, which is fixably attached on the upper side of the heating bottom plate 3, and has a Ta--Al heating electrode 4 on its middle, a diaphragm 7 having a spacer 6 and fixably attached on the top circumference of the Al-electrode 5, the diaphragm 7 being made of, for example, copper (Cu), attaching layers 8, 9(referred to as "filler"), placed between the top of the Al-electrode 5 and the bottom of the spacer 6, and between the top of the spacer 6 and the bottom of the diaphragm 7 respectively so as to improve the adhesiveness between them, an expansion agent 10, which fills the space between the Al-electrode 5 and the diaphragm 7, a sealing bottom plate 11 fixed on the bottom of the heating bottom plate 3 for shutting down the expansion agent opening 2.
In FIG. 1, reference numeral 12 identifies a power line.
The cap 1 comprises a space 1a occupying a certain space there inside for passing liquefied coolant, and an inlet 1b and an outlet 1c on its top, the liquefied coolant being in communication with the space 1a through the inlet 1b and the outlet 1c.
The flow control valve of the throttling type is constructed in a manner that the Al-electrode 5 having a Ta--Al heating electrode 4 is fixably attached on the top of the heating bottom plate 3, and a lower attaching layer 8, the spacer 6, a upper attaching layer 9, and the diaphragm 7 are sequentially attached on the top of the Al-electrode 5 thereby forming a certain space inside the Al-electrode 5, the spacer 6, and the diaphragm 7.
Then, an expansion agent 10 is induced through the expansion agent opening 2 on the bottom of the heating bottom plate 3, the expansion agent opening 2 is sealed by fixably attaching a sealing bottom plate 11 on the bottom of the heating bottom plate 3, the sealing bottom plate 11 is fixably attached on the bottom of the cap 1, and the power line 12 of the Al-electrode 5 is taken out of the cap 1.
The center of the diaphragm 7 is placed directly under the outlet 1c formed on the cap 1.
In the conventional flow control valve as described above, liquefied coolant is induced through the inlet 1b of the cap 1, passes through the space 1a there inside, and discharged through the outlet 1c to the evaporator. When controlling the flow of the liquefied coolant, power is applied on the Al-electrode 5 through the Ta--Al heating electrode 4 of the Al-electrode 5, the Ta--Al heating electrode 4 of the Al-electrode 5 emits heat, and the expansion agent 10 filling the Al-electrode 5, the spacer 6, and the diaphragm 7 is expanded so that by the heat expansion of the expansion agent 10, as shown in FIG. 2, the center of the diaphragm 7 is expanded toward the outlet 1c of the cap 1, and the whole flow amount of the liquefied coolant is controlled by controlling the amount of the liquefied coolant discharged through the outlet 1c.
However, the conventional throttling type of the flow control valve controls the flow amount of the coolant by heating the Ta--Al heating electrode 4 and expanding the expansion agent 10. However, it has disadvantages, such as the inability to proportionally control the flow. Also, there is a demand for addressing the many difficulties involved with the use of the expansion agent 10.
The above-noted difficulties of use of the expansion agent 10 include imperfection of sealing to completely prevent the leakage of the expansion agent 10 and, the decreased endurance of the diaphragm 7 according to the repeated expansion and the shrinkage of the expansion agent 10. These serve as reasons to decrease the reliability for the flow control valve and shorten the life time of the all components.